1. Field of the Invention
The present invention relates to a pneumatic centrifugal separator for sorting particulate material so that solid particles of a size exceeding that of a predetermined dimension are separated from a flow of solid particles suspended in a stream of gas, which separator comprises guide vanes disposed along the generatrices of a fictitious cylinder having a vertical axis, the guide vanes being adapted to impart to a gas stream entering the fictitious cylinder a rotary motion about the vertical cylinder axis, a rotor coaxially positioned in the interior of the fictitious cylinder, the rotor being equipped with a set of vertical blades distributed uniformly along the periphery of the fictitious cylinder, means for introducing a gas stream and particulate material to be sorted between the guide vanes and the rotor, and a central outlet through which the gas stream charged with particles of dimensions smaller than the predetermined dimension and sorted out of the particulate material is drawn out.
2. Description of the Prior Art
A separator of this general type has been disclosed in U. S. Pat. No. 4,689,141. In such separators, the particles suspended in the gas stream are subjected to two opposing forces: a centrifugal force resulting from the rotary motion and a drawing force resulting from the centripetal flow of the gas stream towards the central outlet. The separation of the large particles is effected at the cylindrical outer surface of the rotor. If the distribution of the gas stream over the entire height of the turbine rotor is uniform, there is a single critical or cut-off particle diameter determining the sorting of the particles, which corresponds to that of a particle in equilibrium on the exterior surface of the rotor. The particles having a diameter exceeding the critical or cutoff diameter are thrown back against the guide vanes by the centrifugal force and fall by gravity into a collecting hopper positioned below the guide vanes. The particles whose diameter is smaller than the critical or cut-off diameter are entrained by the gas stream across the rotor towards the central outlet.
In the known separators of this type, the rotor is equipped with rather small blades along its periphery and, in operation, a vortex is formed in the center of the rotor, in which a substantial part of the kinetic energy of the gas stream is dissipated.